I think the 1.4 is a must have for full frame owners. Agree 400 is out of the question for just about everyone. Unless your sports illistrated that buys them for their staff to use at the olympics

I use the 1.4 all the time with my 1Dx2 and the 300 and there is negligible loss in performance as compared to the 7D2. Even with a 1.4 the 1Dx2 Blows the 7D2 out of the water with AF performance and tracking. So much so that Im only using the 7D2 for reach needs and stationary and larger subjects like elk and bears, coyotes and big birds that are not on the move. Its night and day difference with 1Dx2 and 7D2 tracking capabilities.

I have the Sigma 2.0 TC and it seems to perform better than the canon in my opinion. I rarely use the 2.0 and only break it out when I have other choice. The grizzly I got at Yellowstone with a 7D2 and a 150-600 comes to mind. It was the only way to get me close. I was a6 600,, on the lens, with a 2.o TC, and the 7D2 manual focus....Got him but nothing i would print. This is the shot with the 7D2

This is also a fairly large crop. But you could print bigger than 8x12 for sure

Thanks for all of the responses, there was a near new 1.4 iii going reasonably cheap in my area but someone snapped it up, against most of your recommendations I've picked up a 2x iii at a great price ($290 use) so I'll treat it as a hireage and if it's no good I'll pass it on at a slight loss and hope to find a 1.4 iii that will work better

James P wrote in post #18583797I'm afraid that you're the one who is mistaken. I have this combo. Do you?

Any f2.8 lens with a 1.4x will auto focus with those cameras (f4). If they do not for you, then there is something else at work there. If the two cameras cannot focus with f4 on more than center AF points, there is a problem.

James P wrote in post #18583797I'm afraid that you're the one who is mistaken. I have this combo. Do you?

I don't need to own gear to know that a 1.4X TC reduces aperture by 1 stop. Both f/2.8 lenses become f/4 when paired with 1.4X TC. It is physics, not gear ownership. Look again. You can mount your own f/2.8 lens with your own 1.4X TC and dial in f/4 on your own camera. Why you didn't try that before posting completely escapes me, since you have the gear.

James P wrote in post #18583797I'm afraid that you're the one who is mistaken. I have this combo. Do you?

Bassat wrote in post #18583910I don't need to own gear to know that a 1.4X TC reduces aperture by 1 stop. Both f/2.8 lenses become f/4 when paired with 1.4X TC. It is physics, not gear ownership. Look again. You can mount your own f/2.8 lens with your own 1.4X TC and dial in f/4 on your own camera. Why you didn't try that before posting completely escapes me, since you have the gear.

Wondering if there might be a misunderstanding re which lenses are being referred to; the OP states 300f/2.8 L IS and a 70-200f/2.8 L IS ii, but James' sig shows a 70-200 f4 and 100-400L (but not the 300L or 70-200II)?

As noted; an f/2.8 lens with a 1.4x TC "loses" one stop (f2.8x1.4 = f/4) and will AF on any body. An f/2.8 lens with a 2x TC becomes 2.8x2 = f/5.6, and will also AF on any body.

An f/4 with a 1.4x TC is f/5.6; again ok. With a 2x it'll be f/8 - so restricted on compatible bodies re AF.

As the 100-400 is f/5.6 at the long end, even a 1.4x TC pushes it into f/8 territory.

Liveview AF is more forgiving; I believe it'll work down to f/11, at least on the newer Dual Pixel AF bodies.

Like the OP I use the Canon 300 F2.8 L IS, 1DX and both 1.4 and 2 x Mk3 extenders - I have lots of AF points at F4 and F5.6. Pretty good AF too even with the 2 x so long as the light is decent.Perhaps there is something wrong with your setup?

Life is for living, cameras are to capture it (one day I will learn how!).

James P wrote in post #18584341You are correct, sir. My combo is a 1Dx, 1.4 extender with a Canon 100-400 II. With that gear I get center focus point only at f/8. My apologies to those I have apparently offended.

You didn't offend anyone, but the info you supplied (pertinent to you) wasn't very pertinent to the individual that posted the question or others that are reading this thread or replying to the OP, thus the comments.

This site has a good reference table of what cameras have f8 and how it is managed. The 7D2 has center plus assist points, the 1DX only the center... for example. One has to remember that a 1.4x reduces the light by 1 stop (so f4 now produces f5.6 equivalent light) and a 2x reduces the light by 2 stops (so f4 produces f8 equivalent light). I only supply this for those that are reading this thread trying to figure out whether a TC is good for them as well.

So my 2x iii Arrived today and I had half an hour or so to play around with it before dark and so far i'm impressed, the AF has slowed a bit but that was to be expected, sharpness looks fine. Can't wait to test it out on the Rugby field this weekend

Milutiche wrote in post #18585938So my 2x iii Arrived today and I had half an hour or so to play around with it before dark and so far i'm impressed, the AF has slowed a bit but that was to be expected, sharpness looks fine. Can't wait to test it out on the Rugby field this weekend

The cat especially looks good for what is a wide open shot. You should see a little bit of improvement by stopping down. My 70-200 benefits from f/8 or f/11 with the 2x TC; the 300L may do fine with f/6.3. it's worth experimenting to see.

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